Alkenylation of thiophenes



Patented Jan. 26, 1954 UNITED eaten OFF 2,667,496 ICE hKEmA'rIoN or THIOPHENESE- Indiana N Draw ng, ApplicationflDecejmben 30;;1843L Serial No. 1365164 soiaimsa (01. 260-329) This, invention relatesito, the alkenylatiorrv of aromatic. heterocyclic compounds: having a;-. su;1;- fur, atom in the, heterocyclicringi-r Theseoom: pounds include thiophen th tol ne'itth px nes and; t ona htbeneo he-. nye tionr lates; more part c y to; her epa ation m noa ken l ophene and. monoallsenyles itrated hic- Phenes by h ata yzed r act q a: hiorhe 0 he above, pe; w th a .c iusatm; diqleiimc hydroc r on:

A s. e k wn t e, fi-member dheter cycnc n n ti u n hiqpheneie. a r lative i-stah e m n nw ich. n? arbq r oul r; onds e h' fiebst r dil brq er- Conse u nt ca q. e ts hich wo ld. befiective i nt oduce. a substituent for' a hydrogen on' the ring tend to decompose the compound and produce hydrogen sulfide and polymers. Itis also known thatv thev a tan i 'efie pr i r lr 9min.- e t' d le s, are a ily, mlymerized n, h presence of strong catalysts, suoh for, example, assulfuric acid.

' As disclose dand claimed-in the copending application of Becker, Serial No. 135,319, filed De cember 2'7, 1949, sulfonic acids, preferably, alkanesulfonio acids, can be employed tocatalyzethis alkenylation reaction in, whichthienyl alkenes,

particularly monoalkenyl thiophenes, are produced, provided that thefreaction temperatureis maintained below about 0f C.

It is a primary object of thepreserit invention to provide a process of alkenylating thiophene and substituted derivatives thereof, at substantially ambient temperaturesso that,cooling requirements can be greatly, reduced, Another objectof the invention is the proyision of a meth: r p ari m noa lkenyl o h n' sh d o ken lub t ute .thio hen sa he nvene tiori has f r, h r j t uch. ther y nr tages or results as will appear in the specification or the claims hereinafter made. I

Briefly stated, the present invention comprises reacting thiophene or asubstituted thiophene with a conjugated diolefin at temperatures between 0 and 80 C., and preferably at-- temperatures-between 5 -and50'-C., in-the-presence of at-least l-percent by weight, based on the-thiophene compound, of sulfonic acid-oxonium saltcon-iplex catalyst-that is stable under reaction-conditions and. is formed-by mixing a-sulfonic- -acid-andan aliphatic orcyclicether havingwnot more than about 12- carbon atoms. Suitable ether com-'6 pounds are dioxane, alpha-pyrone, tetrahydroranr:diethvla iprop lia butyl ether- Preferably-a mo1arexcess of thiophene or thiophene derivative is employed. A molar excess of thiophene does :not produce predominantly .dithienyl I alkanes byreaction withadiolefinas might be expected, but rather the monoalkenyl thiophene is produced in predominant-yield. Contact of-the diolefin andthe catalyst-.complex--before admixture withthe thiophene reactant-should 31b avoided to-prevent- -polymerizatiomoi the dio1efin-.---

Preferably; thethiophene? compound and the cat'- alyst are; first mixed,- and th'em the 'diblefin" is slowly addedv to the mixturewhile-- cooling" the same toremove exothermic heat or reac'tioni In one alternate method, a) mixture of .the thiophene compound; and" the oonju'gatedi, diolefin:= can; first be prepared and :the catalyst complex canbe slowly; added'to theamixtur'eh In another method, a mixture of thethiophen'e':compound-and the sulfonic acidoxonium'a salt: complexis': first: prepared andlthemis' addedzto amixthrecofithe:t'hiophene compoundandth'e diolefim Although the process can be;efiectively operatedtati atmospheric pressure, it is; preferred: to-employ mildi superaatmospheric pressure, particularly: when: operating'within the upper; portioneof the range." of op-. erating tem eraturesghereinabovezset forth:r Sue peratmospherio pressuressareemployed to ensure liquid phase reactiornrparticularly: when .the di-;- olefin is of I low moleculariweight, for: example; butadiene; I The I rate, of; reaction: appears to; be substantially, instantaneous-, but-it; is; necessary to add the diolefin; slowlyrenough-toavoid de:-' veloping. excessive: temperatures; ThUSpISfiCfiOIl can be completed within less-=than,; .for example, twenty minutes, but if 6 they cooling, capacity--- is limited, a, reaction periodi ofg one-halfato three hours can be employed.

The employment or the. dioxanesulfonicacid complex as the alkenylation catalystpermits. not onlyareaction at practicable and readily-,controllable .,temperatures,,but 6 alsq, providess assubstantial -yield,.o the ,monoalkenyhthiophenes; (thieny-1 alkenes) it, avoids the. polymerization of 6 the employed conjugateds diolefins which, hasE-here-e tofore been observed ,andgis .to ibe expected when strong acid condensation agents areoto beiemployed and also .the deeompositionpor polymerzation. of the thio h n e m' ounda The employment of ,alkane, sulfonicflacidlcoma plexes which the. alkane group has. atmostfive carbon atomsaper, m01ecule,provides.,an.ease of separation of catalyst from vthe, resulting, a1: kfinylated oils inasmuch ,as, these.,acids,- are pref erentially water-soluble. Thus, itis preferred .to employ the addition compbundsoffdioxane and methane-, ethane-, l propane Z-propanee, l-butane-, 2-butane-, 2-methyl-2=p ropane, or pentane-sulfonic acidsor mixtures thereof," e. g., a commercially available mixture of,Ci-C alkanesulfonic acids There can, however; be employed higher-alkanesulfonicacids such' as 'octane decane-, dodecane-sulfon-ic@acids findthQlikBI One can also employ aromatic"sulfonidaoids-such"as benzene, toluene xylene naphthalene sulfonic acids,- andthe like;- other fsulfonigacids"avail; able; for-use in th'e practice of purinvention-am cycloalky-l sulfonicacids; such as" cycloh'exane sulfon' ic and methylcyelohexanesulfonicacids-and the like. Aralkylsulfonic acids: such" as 'b'en'zylf sulfonic, beta-phenethylsulfonid acids and {the likecan also befused.

Diole'fiiisparticularlysuitabie imthe present re action include those conjugated diolefins such, for example, as 1,3-butadiene, isoprene, piperylene, 2,3-dimethylbutadiene, cyclopentadiene, methylcyclopentadienes, 1,8-cyclohexadiene and 2-chloro-1,3-butadiene. As aforementioned, the thiophene compounds can include thiophene, C4H4S, thiotolene, C5H6S, the thioxenes, CsHaS, and thionaphthene, CsHsS. In the case of the thioxenes, those isomers in which an alpha carbon atom is available to the alkenylation reaction provide better yields and thus are preferredin the process.

Thiophene, the leading member of the heterocyclic series, is found in small quantities in coke oven light oil and can be prepared by reaction at about 600 C. between butane, such as that obtained from the C4 cut from petroleum cracking processes, and sulfur. Butene, butadiene, thiophene, and hydrogen sulfide are the products of this reaction. Butadiene can be produced in varying relative quantities of from about one-half to one mol per mol of thiophene.

Under reaction conditions, about 1 percent of dioxane-sulfonic-acid addition product by weight based on the reactant heterocyclic sulfur compound is required to effect reaction. Amounts of catalyst above 40 percent by weight based on the heterocyclic reactant efiect no increase in catalysis and at higher concentrations undesirable side reactions may be encountered. A preferred range of catalyst concentration is from 2 to 20 percent of sulfonic acid-oxonium salt complex by weight, based on the heterocyclic sulfur compound. In spite of the known tendency of strong acid condensation agents to effect polymerization, the above concentrations of the sulfonic acid complexes, either as chemical individuals or as a mixture of complexes of the acids having not more than 5 carbon atoms per molecule, result in substantial production of monoalkenyl thiophenes.

The following example will illustrate the process of invention.

The oxonium salt complex of a mixed alkane sulfonic acid and dioxane was formed by mixing 0.47 mol of the mixed acids, which contained methane-, ethane-, propane-, and a small amount of butanesulfonic acid with 0.47 mol of paradioxane. An addition product formed with evolution of heat.

The so-formed dioxane alkane sulfonic acid catalyst was added to 252.3 grams of thiophene. Isoprene was then slowly added to thiophene catalyst until a total of 68.1 grams of the diolefin was consumed. The temperature was maintained between 25 and 30 C. Thienyl pentene in a yield of 49 percent of the theoretical yield was obtained. The so-produced thienyl pentene (boiling point 121 C. at 60 mm. Hg; n 1.5255) was found to have a molecular weight of 152 by mass spectrometric analysis corresponding to 152, the calculated molecular weight of monomeric pentenyl thiophene. The mass spectrum observation provided no evidence to indicate the presence of compounds of any other molecular weight in the separated product.

As illustrated in the foregoing specific example, at least one mol of ether per mol of sulfonic acid is employed in forming the ether-sulfonic acid complex, or addition product. The mol ratio of at least 1:1 is required to avoid the presence of any free sulfonic acid in the so-produced catalyst. An excess of ether can be used and preferably a mol ratio of ether to sulfonic acid of from 1.2 mols/mol to 1 mol/mol is effectively employable in the formation of the catalyst. The catalyst is formed by mixing the components, either one of which can be added to the other. In either case the heat of formation should be removed to an adequate degree to prevent excessive heating.

The thienyl alkenes are useful in the preparation of copolymers, in esterification processes and as organic intermediates.

We claim:

1. The process of preparing thienyl alkenes that comprises reacting thiophene and a conjugated diolefin at a temperature between about 0 and C. in the presence of at least 1 percent by weight based on the thiophene of a nonolefinic hydrocarbon sulfonic acid-oxonium salt complex catalyst that is stable under reaction conditions and is formed by mixing a saturated ether having not more than 12 carbon atoms and a non-olefinic hydrocarbon sulfonic acid.

2. The process of alkenylating a thiophene compound having an available hydrogen-substituted alpha carbon atom that comprises admixing a said thiophene compound, a conjugated diolefinic hydrocarbon, and at least about 1 percent, by weight based on the thiophene compound, of a catalyst that is a dioxane-alkanesulfonic acid addition product, maintaining the thiophene and diolefin at a temperature between 0 and 80 C. and efiecting reaction therebetween.

3. The process of preparing thienyl alkenes comprising passing a conjugated diolefinic hydrocarbon into a molar excess of thiophene containing between 2 and 40 percent by weight, based on the thiophene, of catalyst consisting of a dioxanealkanesulfonic acid addition product of which the acid has not more than 5 carbon atoms per molecule at a temperature between about 10 C. and about 50 C. for a period of time sufiicient to effect substantial completion of reaction between thiophene compound and diolefin, separating liquid product from the catalyst, and recovering a thienyl alkene from the product.

4. The process of claim 3 in which the conjugated diolefinic hydrocarbon is butadiene.

5. The process of claim 3 in which the conjugated diolefinic hydrocarbon is isoprene.

6. A process of alkenylating a thiophene compound having an available hydrogen-substituted alpha carbon atom that comprises admixing a said thiophene compound and a conjugated diolefinic hydrocarbon at a temperature between about 0 and 80 C. in the presence of at least about 1% by weight based on the thiophene compound of a non-olefinic hydrocarbon sulfonic acid-oxonium salt complex catalyst that is stable under reaction conditions and is formed by mixing a saturated ether having not more than 12 carbon atoms and a non-olefinic hydrocarbon sulfonic acid.

7. The process of claim 6 in which the conjugated diolefinic hydrocarbon is, butadiene.

8. The process of claim 6 in, which the conjugated diolefinic hydrocarbon is isoprene.

ARTHUR A. HARBAN. CARL E. JOHNSON.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,141,611 Malishev Dec. 2-7, 1938 ..396.1 A e o M 1 .6 2,462,793 Lee Feb. 22. 1949 

1. THE PROCESS OF PREPARING THIENYL ALKENES THAT COMPRISES REACTING THIOPHENE AND A CONJUGATED DIOLEFIN AT A TEMPERATURE BETWEEN ABOUT 0* AND 80* C. IN THE PRESENCE OF AT LEAST 1 PERCENT BY WEIGHT BASED ON THE THIOPHENE OF A NONOLEFINIC HYDROCARBON SULFONIC ACID-OXONIUM SALT COMPLEX CATALYST THAT IS STABLE UNDER REACTION CONDITIONS AND IS FORMED BY MIXING A SATURATED ETHER HAVING NOT MORE THAN 12 CARBON ATOMS AND A NON-OLEFINIC HYDROCARBON SULFONIC ACID. 